Disclosures: O'Dell reports no relevant financial disclosures.
August 19, 2020
4 min read

Cast a wide net for Demodex to serve patients, practice

Disclosures: O'Dell reports no relevant financial disclosures.
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Some patients present with specific complaints and describe distinct visual disturbances or irritation, while others are more like an abstract painting awaiting interpretation. Demodex patients are equally represented in both categories.

Demodex is a pervasive but often overlooked disease seen widely throughout the entire population. It is most prevalent in older patients and those with blepharitis. In fact, infestations of this ectoparasitic mite are seen in 84% of the population at age 60 years and in 100% of those older than 70 years (Liu et al.). Notably, 42% of all Demodex patients are also diagnosed with blepharitis (Dadaci et al.).

Clinical image showing a close up of demodex on eyelashes

The classic presentation of individuals affected by Demodex blepharitis includes cylindrical, waxy collarettes. Source: Leslie E. O’Dell, OD, FAAO

Pervasive parasites

Leslie E. O'Dell, OD, FAAO

Demodex is associated with many conditions, including the aforementioned blepharitis as well as rosacea, meibomian gland disease (MGD), chalazia and ocular surface inflammation.

The majority of Demodex patients have mild-to-moderate symptoms, including itching and burning of the eyes and lids, foreign body sensation and fluctuating blurry vision. However, Demodex is not always symptomatic, so even in the absence of complaints, it is wise to check for the presence of these mites, which, if untreated, can lead to worsening blepharitis, MGD or other ocular surface disorders.

Two distinct Demodex species contribute to blepharitis: Demodex folliculorum and Demodex brevis. Demodex folliculorum reside in the lash follicle and consume epithelial cells, which can cause anterior blepharitis associated with eyelash disorders. They produce follicular distension and hyperplasia and increase keratinization, leading to cuffing at the base of the cilia.

Demodex brevis are harder to isolate and thought to be present within sebaceous glands; they can block the orifices of meibomian glands, resulting in MGD with lipid tear deficiency.

Making the diagnosis

The classic presentation of individuals affected by Demodex blepharitis includes cylindrical, waxy collarettes — also known as cylindrical dandruff — at the base of the eyelashes. Collarettes are a pathognomonic finding for Demodex. Without even removing or examining an eyelash, if you see this waxy cylindrical dandruff, you should consider Demodex blepharitis in your differential diagnosis.

At this point, you may want to epilate a lash and examine it under a high-powered microscope. This will enable you to image and document the extent of the mite infestation so you can track progress once treatment begins. It also provides a concrete visual to share with your patient upon diagnosis and throughout the treatment process.

I also encourage doctors to do a closed-eye exam at the slit lamp. When you see collarettes, you should initiate treatment to counter inflammation even if the patient is not experiencing typical Demodex blepharitis symptoms. It is possible that you are catching it before symptoms are present or that the Demodex has been there so long that the patient has become inured to the symptoms.

Treatment, follow-up

Familiarity with Demodex’s ontogenesis is pertinent to effective initial treatment timing and follow-up. The lifecycle of the Demodex mite is approximately 14 to 18 days from the egg to the larval stage, followed by 5 days in the adult stage (Liu et al.). It is typically most beneficial, then, to initiate treatment during an in-office visit, then schedule a follow-up visit for 2 weeks later.

For in-office treatment, you can initiate with a microexfoliation procedure to begin the removal of collarettes. However, at-home treatment will also be necessary. Until recently, at-home Demodex treatment involved a variety of homespun remedies, such as baby shampoo scrubs and warm compresses, which temporarily soothed symptoms but did not eradicate the mites. Since then, tea tree oil (TTO) has been found to effectively resolve Demodex-related ocular symptoms; however, its use sometimes causes irritation and may impede healing in some patients (Su et al.). Scientists have identified terpinen-4-ol (T-4O) as the most active ingredient of TTO and isolated it for the safe and effective treatment of Demodex (Tighe et al.). Studies show that T-4O helps eradicate Demodex mites and reduce ocular surface inflammation while also providing antimicrobial and antifungal coverage (Hart et al., Brand et al.).

T-4O is effective in both cleaning cylindrical dandruff from the roots of lashes and stimulating the migration of hidden mites to the surface for eradication (Cheng et al., Tighe et al.). In a clinical study, Cliradex (Bio-Tissue), a formulation with a high concentration of T-40, effectively killed all adult mites within 40 minutes of exposure (Su et al.).

Look for Demodex blepharitis even in the absence of symptoms using both microscopic evaluation and a closed-eye exam to evaluate for the presence of collarettes. Employ imaging or other visuals to educate patients about Demodex blepharitis and its associated risks, including localized inflammation, thinning or loss of eyelashes, and damage to the lid margin. Reassure the patient that Demodex is a common occurrence not associated with personal hygiene. Alleviate their concerns by explaining that Demodex is much like bacteria in that it resides on the body and can become problematic if it is present in an overabundance.

Treatment with T-4O covers all the bases from eradicating the mites and associated inflammation to treating or preventing any existing or potential infection. By embracing treatment of this pervasive disease, you have the opportunity to improve the ocular health of your patients and pave the way for an additional revenue stream for your practice.

For more information:

Leslie E. O'Dell, OD, FAAO, is the clinical director of Medical Optometry America in York, Pa., and a global ambassador of the Tear Film & Ocular Surface Society, Boston. She can be reached at: helpmydryeyes@gmail.com.